ID 79

Large Eddy Simulation of a Turbulent Ethanol Spray Flame under MILD conditions using a Finite Rate Chemistry Combustion Model

 

Abstract:

Numerical simulations of the Delft Spray in Hot Co-flow (DSHC) flame are presented, in order to validate an Euler/Lagrange multiphase combustion framework under Moderate or Intense Low-oxygen Dilution (MILD) conditions. Special emphasis is put on the influence of spray boundary conditions on such flames. The test case consists of a single pressure swirl atomizer installed in the center of a cylindrical hot co-flow, operated with liquid ethanol. Three operating conditions (HI-HIII) with different co-flow temperature, velocity and oxygen concentration are simulated by means of Large Eddy Simulations including a Finite Rate Chemistry combustion model in combination with a detailed chemical reaction mechanism. The discrete phase is modelled in a Lagrangian framework using a point droplet approximation. Different formulations for the spray boundary condition are derived from downstream measurements of the spray and compared in the simulations. The results obtained show excellent agreement for both the continuous and the dispersed phase over all operating conditions. Radial distribution of droplet Sauter Mean Diameter and droplet velocities at various axial locations are accurately predicted, gas phase velocity matches well with experimental data. Gas phase temperature and its fluctuation are in good agreement with the experiment. However, a strong influence of the formulation of the spray boundary condition on the temperature around the vertical axis is present due to fast evaporation of small droplets. Yet, it is concluded that the used simulation framework and combustion model is able to accurately predict all features of spray flames under MILD conditions.